Hi, I am running into an issue where some code that compiled and worked under 6.12 is failing under 7.0, the offending code is class DeNameable a where deName :: Module -> a -> a getDeName :: Tc (DeNameable n => n -> n) getDeName = do mn <- asks (tcInfoModName . tcInfo) return (\n -> deName mn n) Tc is a plain typechecking monad and this returns a generic denaming function that can be used to turn haskell names back into human readable form before printing errors in jhc. I have the ImpredicativeTypes LANGUAGE feature turned on. the error I get under 7.0 is src/FrontEnd/Tc/Monad.hs:131:29: Couldn't match expected type `n -> n' with actual type `DeNameable n' In the second argument of `deName', namely `n' In the expression: deName mn n In the first argument of `return', namely `(\ n -> deName mn n)' John